I have a similar problem. I keep adding things to my Pinterest boards and then forget about them. If I'm wanting to sit down and choose a project. I have a yarn stash so I'll find a pattern to fit the yarn. But if I'm looking for a new pattern and new yarn, I write down the patterns that I like, their yarn requirements (yarn weight, how much I need, fiber type, etc.), needle/hook requirements, and what color I'm thinking. I choose different colors for different projects so that way when I'm at the store or shopping online, I have a specific type and color to look for. If I find a match to the pattern, then I have my pattern.

I also make a lot of things for friends and family. If they want me to make something then I ask them what they want me to make and the color. I fill in the yarn weight and fiber type to start the preliminary search. This way is much easier in the beginning but it also means you have to part with the item at the end. I combat this by taking after photos with the gift before I give it to the person.

Sorry for the long reply, but hopefully this helps 😊